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A Ni3AI + B base composition and derivatives containing Hf, Zr, Nb, or Nb + Hf substitutions for Al were processed by powder metallurgy, consolidated by compaction + extrusion, and evaluated for mechanical properties. The mechanical property evaluation consisted of tensile tests performed in air and vacuum, and fatigue crack growth tests performed in air. Microstructures, test specimen fracture morphologies, and tensile and fatigue deformation features were also studied. Some of the substitutions improved certain properties, but none improved ductility. The discussion considers property-fracture morphology-deformation structure relationships.

A detailed study of deformation of NiAl single crystals in two soft orientations, <110> and <111>, has been conducted. The Schmid factor favors {100} slip in the former and {110} slip in the latter. Detailed dislocation analysis, critical resolved shear stress measurements, and slip trace analysis have been performed to determine the nature of dislocation motion and interactions in this material. Particular attention is given to prismatic loops formed during deformation, since the shapes of these loops reveal the active slip planes. Similar loop morphologies observed in elevated temperature [001] oriented tensile specimens are also discussed.

A four-year survey of high-temperature intermetallic compounds has been aimed at identifying potentially useful structural materials for aerospace and aircraft engine applications. Since the good properties of high strength and stiffness at high temperatures are typically negated by brittleness at ambient temperature, new materials must have roomtemperature toughness or ductility. Screening has been done of 90 binary compounds with 20 different crystal structures, and 130 ternary or higher-order alloys. Testing typically included hardness vs. temperature, elastic modulus determination, and toughness evaluation via a room-temperature chisel test. Four alloy systems, including only two types that are of the simplest structures, showed substantial room-temperature toughness: Al-Ru, Ru-Sc, Ir-Nb, and Ru-Ta. Of these the last and the first are the most promising. Special features of the Ru- Ta (L1o) alloys are their room-temperature impact resistance and high-temperature strength. AIRu (B2) alloys can be tougher than the L1o structures and most are also ductile in compression at room temperature. Alloying experiments with B, Cr, and Sc show beneficial effects on ductility, oxidation resistance, and high-temperature strength.

In this study, the strain rate sensitivity of single crystal NiAl has been investigated by performing tensile tests as a function of temperature and two strain rates. Three crystallographic orientations, [100], [110], and [111] were studied. The tensile test results investigated include yield strength, work hardening rate and plastic strain to failure. The data are discussed in terms of deformation mechanisms in NiAl.

An investigation was performed to study the origin and stability of microstructures in rapidly solidified aluminum alloys. Al-Ni and Al-Fe base alloys were rapidly solidified by means of laser surface melting and melt spinning techniques. Microstructures were studied using optical and transmission electron microscopy. The effect of microstructure on mechanical properties was also studied using microhardness measurements. The origin of the observed microstructural constituents will be explained in terms of features of the metastable phase diagram. The effect of ternary additions on stability will also be considered.

Alloys based on the B2 compound NiAl have significant potential for applications in hot sections of aircraft engines due to their low density, high melting point, and high thermal conductivity. A major disadvantage of this class of materials is low ductility at ambient temperatures. Recently, it was discovered that small levels of certain elements (eg. Fe, Ga, Mo) result in dramatic improvements in room temperature ductility. In this paper, results are presented from a mechanistic investigation of the “microalloying” effect. Tensile and compression testing as a function of temperature and orientation has been performed on both the binary compound and microalloyed material. Data on ductile to brittle transition temperatures, critical resolved shear stress values as a function of temperature on the different slip systems, and dislocation structures from TEM analysis of the tested specimens are presented. These data are discussed in terms of possible mechanisms for the microalloying effect in NiAl alloys.

In this study, the room temperature tensile properties of a single crystal NiAl alloy were investigated as a function of orientation. Fifteen crystallographic orientations were tested, including the <001>, <110> and <111>. The tensile properties measured include yield strength, plastic strain to failure, and ultimate tensile strength. Room temperature ductility as high as 1.4% was measured as close as 10° from the <001> orientation.

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